Ok, I filled two white nylon knee-highs today with Seachem Matrix. I put one in my 125, and one in my 40B. The one in the 125 still looks the same tonight, but the one in the 40B has turned bright pink! (the knee-high). What's up with that? Where the nuggets of Matrix press against the nylon they look normal colored, it's just the nylon itself that turned bright pink (as far as I can tell). I'm going to buy more knee-highs tomorrow at work & switch it out.

So I did an experiment last night before I went to bed - I put a folded paper towel in the tank, held tight by the glass top just like the stocking, and I also folded the top of the stocking back into the water (no Matrix in it, just the nylon). Both were pink this morning.

It dawned on me that it must be dyes leaching into the water from the substrate. That tank was set up before I ever knew about dirted tanks, and it's a mix of natural color gravel and CaribSea FloraMax. My guess is it's the FloraMax, which isn't quite the same dark color it used to be. Guess I'll be hanging a HOB with Purigen on that tank when I get home from work tonight! But what a shock it was to walk into the room and see that last night - lol.

I've never used Floramax, or heard anyone else report this problem. The reason I asked if it was black:

A few years back I experimented with dyeing substrate, using homemade concrete stains. Iron for red, manganese for black. The manganese, if highly diluted, can appear pink or purple.

I was just binding these elements to a thin outer layer. Substrate that comes colored from the manufacturer normally has it through and through. But I suspect the same elements are responsible for the colors in all substrates, regardless of whether it's made in a kiln or mined from the earth. I know that the elemental analysis for Flourite Black has much more manganese than the other colors.

It should be bound and stable. Not sure why it would start leaching out to the point of being noticed, if that is what's really happening here. I'm guessing it will stain Purigen, perhaps permanently; but being inorganic, Purigen should have no special affinity for removing it.

That's very interesting! I wonder if the age of it has anything to do with it. Since that's the only tank its happening in, I bet it is the FloraMax - which is only in that tank. I'll be breaking it down in a few months and I'll scrap the substrate then.

Coincidentally, I just rebuilt a tank using a fresh bag of Flourite Black. If manganese leaching occurs, I figured brand new and dusty substrate should release an initial burst. So I tried your paper towel experiment:

The characteristic purple shade is almost certainly proof of manganese. I left it in for two days, and forgot to check on it in the meantime; but if I had, I'm pretty sure it would have been a lighter shade of pink.

So basically a hob full of cotton balls, or some cottony material would be best suited to absorb the dye. No?
Cotton pillow batting?

I'm not sure if it's really fair to call it a dye, or if removing it would serve any purpose.

CSM+B contains 2% manganese, a necessary nutrient. It's probably EDTA chelated in that source, so I don't know if plants can directly or efficiently utilize what the substrate is releasing.

Manganese is toxic if overdosed, the Wikipedia article and MSDS for manganese dioxide are rather scary to read. That's the reason I never pursued dyeing substrate at home on any useful scale, only a few small test batches to satisfy my own curiosity.

It's certainly eye-raising to see enough manganese in a tank to be detected with a mere paper towel.

But I'm not going to panic, or suggest anyone else do so either. If this was a significant issue, I'd imagine we'd have noticed a few "Flourite Black killed my fish" threads by now, right?

Thought you'd get a kick out of my white knee-high. Mind you, it started turning pink with 6 hrs, and was this saturated by the next day. You can see there is still some white - that's the only part that never came in contact with the water.

The second pic shows my gravel - yes, it's ugly! lol. I set this tank up before I new about the beautiful creek bed gravel locally, and I was just learning about live plants. It's a mix of equal parts Midnight FloraMax, Natural FloraMax, and ordinary pea gravel from Lowes. Set up close to 4 years ago. Once I get the new sub flooring and pine flooring down and the 55 and 90 set up, this tank is getting a remodel - lol.

I'll have to put some water in a white plastic cup and see...I've thought for a long time now that the 40B just doesn't look right. It doeasn't have any driftwood, so I couldn't understand the dingy look - even though I do my scheduled water changes, etc. I thought the multi colored gravel was playing tricks on my eyes. I'm going to put some in a glass now & look...lol

The water does have a noticeable tone to it - but I can't say it's pink! Whereas the cup is bright arctic white, the water has a faint vanilla tint. Probably just because tomorrow is water change day - haha.

It seems strange that color so vivid would show up absorbed into a nylon stocking, but not be visible in the tank. Mind you, 40 gallons is different than a plastic cup. I wonder if it does effect the fish somehow? These Columbian Tetra fry developed much, much slower than the ones that I left in the tank they hatched in. They are about 3 months behind, size-wise. I chalked that up to the difference in available food and tank size. The flake-only that I fed the 40B fry when young vs. a whole 125 tank's worth of who-knows-what's in there. Also the difference in having 6' to swim in vs. 40". Jeez, every time I think about them I start panicking about getting their bigger tanks set up!

And how about Nature vs. Nurture? The fry in the 125 readily eat bloodworms and peas, spinach and other veggies - they've seen all the adult tetras in the tank do so and learned from them. The fry in the 40B, raised by themselves, only would eat flake until a few weeks ago. Now they eat peas, but won't touch other veggies or bloodworms - they ignore them like they don't recognize them as food yet. I thought that was interesting...

Temperature has a big effect on maturation rates. Even if two tanks are unheated, one will often be a few degrees warmer due to lights, heat from powerheads, etc. Worth checking into, but it doesn't seem to be the only factor. Guppy fry almost always mature faster in my 46G fed once daily, which is my largest and runs about 77°F average on its own; than any other tank deliberately set up for fast maturation, heated to 82°F, and with feedings three times per day. Strange that tank size, scavenged food, and perhaps other unknown factors, seem to overwhelm more direct influences. For a tiny fry, even a 10G is a vast space.

And as for fish learning, it's all cool until one decides to start eating live plants... and others start mimicking it too! I had that happen, fortunately just once, and had to get rid of a few fish to shut it down.

Aquariums are always an adventure. If you do end up changing the substrate and later find that fry mature faster, let me know.

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